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By Harold J. Bennett

The Minerals Availability Program is a Bureau of Mines Program to systematically measure and classify identified worldwide nonfuel mineral resources according to their respective extraction technology, economics, and commercial availability. The program is designed to identify, collect, compile, and evaluate information on worldwide active mines as well as on developed and explored mineral deposits, and on mineral processing plants. Objectives are to classify domestic and foreign resources, to identify by cost evaluations resources that are reserves, and to prepare analyses of the availability of these resources for 34 commodities and secondary minerals. Availability analyses consider such factors as geographic location, the type of producible material, the technology and time required to produce a marketable product, and the productive capacity and unit cost for each deposit. These factors, reflected in the aggregated tabular and graphical data in the study for each commodity, are developed for consideration in the formulation of both domestic and foreign mineral policy. To date, the data have been collected for the 34 commodities and the availability analyses are in various stages of completion; expected first cycle completion date for all 34 is early 1986. Raw and aggregated data are available to the public in the form of computer-generated listings, tapes, and maps as well as in published reports. Also, systems developed to assist in performing the engineering and economic c analyses, including the computerized economic evaluation program (MINSIM) and the cost estimating system (CES), are available.

Jan 1, 1984

By Hans Ehdwall, Erling Strandon, Friedrich Steinhäusler, Victor A. Leach

INTRODUCTION The basis for any measures in radiation protection is the quantitative assessment of the radiation exposure. Due to the extensive requirement in health physics manpower and related cost it is necessary to develop certain criteria regarding the necessity of monitoring and the selection of population groups to be monitored. Depending on the overall objective of the particular programme, the specific requirements for the measurement of atmospheric levels of radon, thoron and their daughters for practical radiation protection purposes differ significantly for those in the case of research applications, such as use of data for epidemiological studies. As part of the OECD-NEA Programme on Radon Dosimetry and Monitoring Task Group 1 reviewed available models for lung dosimetry in the case of inhalation of radon 222, radon 220 and their daughters (James et al., 1981). Using defined reference atmospheres for underground- and open-pit mining conditions as well as for dwellings, normalized conversion factors were calculated for the mean bronchial dose (mGy) per Working Level Month exposure (WLM). Task Group 2 discussed the features and adequacy of the Working Level (WL)-concept as a physical correlative of the absorbed lung dose and its limits of confidence and accuracy (Johnson and Leach, 1981). The WL-concept was found acceptable for radiation protection purposes provided that modifying factors like particle size, unattached fraction and respiratory minute volume did not cause the effective dose equivalent per WLM as calculated by either the James-Birchall or Jacobi-Eisfeld lung models to be more than 50 % above that given by ICRP of 0.01 Sv/WLM. For application in epidemiological studies the WLconcept is considered acceptable if the calculated absorbed dose to the tissue does not vary by more than 50 % (at the 95 % confidence level) from that given for defined reference conditions. In the following, objectives and requirements for the measurement of radon, thoron and their daughters are discussed for operational health physics routine and special research applications according to the scheme outlined in Fig. 1.

Jan 1, 1981

By C. M. Liu

"The Freeport-McMoRan Sierrita Crystal Plant produces Copper (II) Sulfate Pentahydrate (CuSO4·5H2O) through a series of cooling crystallizers. In this process, high supersaturation and unwanted spontaneous nucleation promote fine crystals. Seeding through recycled crystal classification can manipulate the crystal size distribution (CSD) for larger crystals. Proper selection of the crystallizer for seeding can prevent spontaneous nucleation and promote final crystal size. This study shows when seeding temperature is closer to the crystallizer temperature, suspension densities in the crystallizers are promoted and overall CSD shifts to a larger size of crystals. INTRODUCTION Figure 1 shows an overview of the crystallization process. The in-plant feed flow, called Pregnant Mother Liquor (PML), enters the first crystallizer and is subsequently cooled through a series of four crystallizers. Specific temperatures are targeted for each crystallizer to ensure the crystallization process is operating within the metastable zone (MSZ). The discharged flow from crystallizer #5 then enters two cyclones. The overflow from the cyclones contains smaller crystals providing seed crystals for crystallizer #5. The underflow from the cyclones begins the drying process. The overflow from crystallizer #5 enters cyclone #3 for removal of fine crystals and seeding purposes. The underflow from cyclone #3 has the capability to provide seed crystals for crystallizer #1 or crystallizer #2. The overflow leaves the system as Spent Mother Liquor (SML). Undersize crystals dissolve into the PML and return back to crystallizer #1.THEORIES AND METALLURGICAL TESTS Seeding requires an understanding of the crystal size, solution temperature and amount of crystals that enter the crystallizers (1). For the seed crystal size, classified crystal seeds can prevent fine crystals returning back into the system which eventually leads to excessive agglomeration (2). Proper selection of the crystallizer can ensure seeding at an appropriate temperature. Seeding at a temperature much lower or higher than the saturation temperature promotes spontaneous nucleation. Typically, seeding between 4-5°F below the saturation temperature is acceptable (5). A general rule of thumb is to add the seed crystals at the temperature between the solubility curve and the metastable zone. An experiment conducted by Mettler-Toledo AutoChem, Inc. indicates seeding close to the solubility curve rather than the metastable zone promotes a lower supersaturation and nucleation rate but yields a higher growth rate and a greater number of larger crystals (1). The amount of seed crystals can not only change the suspension density but also narrows the width of the MSZ in the crystallizers. An experiment conducted by Jaroslav Nyvlt reports with the crystals absent, the maximum allowable undercooling is 6.3 degrees at a cooling rate, 5°C/hour. With the presence of crystals, it narrows the MSZ width to 2.2 degrees (4). Industrial crystallizers normally operate at suspension densities between 15% and 25% by mass. When suspension densities are lower than 15%, it increases the risk of primary nucleation and the probability of incrustations; on the other hand, if the suspension densities are greater than 25%, it can cause a greater attrition rate and increase the probability of deposits (6). Moreover, operating suspension densities between 15% and 25% are also sufficient to minimize supersaturation rate which promotes crystal growth over nucleation (2, 6)."

Jan 1, 2015

By David G. Van Hersett

The single most unique design feature of the Centralia Coal Mine is the public information program. Just what the heck does public information have to do with the development of a coal mine? The utilities of today have had to build larger and larger plants to keep down the costs of power to the consumer. The large plants require huge amounts of capital, take up large areas of real estate, consume unprecedented amounts of coal, and generate large quantities of waste products which have to be reckoned with. Coal mines supplying these plants have also increased in size and production to meet the power plants' unending appetite for coal. This means the disturbance of great areas of land and significant alterations to the landscape. Today's public is greatly concerned about the environment in which he is living. The great size of a power plant with its large stacks, coal piles, and the coal mine with its large earth movers, disturbed acreages and the resulting waste products of both operations appears to present a threat to his environment. Because of this,' many power plants and coal mines are having public acceptance problems. This has resulted in the passage of stringent legislation and in some cases brought upon construction delays for major power plants.

Jan 1, 1970

By John A. L. Campbell

Are safety concerns justified regarding the potential for a gas explosion due to recirculation when a scrubber is used on a continuous miner? The role of a respirable dust scrubber on a continuous miner section using blowing face ventilation is examined in this paper and the above question answered. Methane control using high efficiency scrubbers coupled with blowing face ventilation is promoted.

Jan 1, 1987

By R. Henley, S. S. Webster, L. Harris

High resolution airborne magnetic and radiometric data have been shown to optimize exploration for epithermal gold deposits in the vicinity of Charters Towers, northeastern Queensland. The radiometric data allow extrapolation of poorly outcropping geology to provide a cost-effective mapping technique, even at exploration scales (eg. 1:25,000). At a regional scale (eg. 1 : 100,000) the magnetic data reflect the regional tectonics and divide the area into domains for the application of different genetic models. For example: 1. the Ravenswood Batholith is characterized by multiple intrusions dating from Ordovician to Permian age. The polarity of the magnetic anomalies implies an age for the intrusions and indicates a deposit style for exploration. 2. extensional and wrench tectonics along the northern margin of the Drummond Basin are interpreted from the magnetic data and indicate favourable blocks for detailed exploration. Genetic exploration models may be tested in favourable environments by the recognition of geophysical signatures. These signatures reflect structural, lithological and alteration patterns arising from controls on ore deposits and can be applied at regional or detailed scales.

Jan 1, 1989

By Yuusaku Tominaga

A flexible expert system for a personal computer has been developed to take countermeasures for prevention of emergency in underground coal mines. The system makes a diagram to estimate maximum airflow rate of a specified branch such as coal face or advancing face, etc. under the conditions of opening regulators set in any two different branches, by computer simulation. The system approximates the ventilating condition underground by using both measured values and safety factor derived from the rules in the system. The probability of happening gas explosion, spontaneous combustion and mine fire underground is shown on a display and countermeasures in a data base in the system are selected according to a confidence factor. When it is recognized in the system that either safety factor or confidence factor of countermeasure has a small value, the system sends information relating to reasoning in the system to registered human experts by computer communi¬cation and facsimile. The replies in file transfer from the experts are stored in the system and reconsultations for estimation of underground condition are started automatically. As the replies in facsimile are shown on the display, user inputs new rules and, values for reconsultation. It is shown that the system is available to take better countermeasures as the condition' of a network in coal mine is changed by mining day by day.

Jan 1, 1992

To gather additional field data from the western United States, researchers from the National Institute for Occupational Safety and Health (NIOSH) installed an array of field instrumentation at a longwall coal mine in Central Utah. The purpose of this field site was to monitor ground movement and changes in pressure during mining where conditions include massive, stiff overburden and relatively deep cover. To accomplish this, field instrumentation was installed in the two-entry gate road between the fifth and sixth longwall panel in the current mining district.

Jan 7, 2020

By J. J. McClellenand, R. A. Jankowski

Face ventilation and water sprays are the primary controls used on continuous miner sections to protect workers from respirable coal and silica (quartz) dust. Laboratory tests were conducted by the U.S. Bureau of Mines to determine the impact on respirable dust concentrations when increasing airflow from 3000 to 9000 cfm (1.42 to 4.25 m3/sec), water flow from 15 to 35 gpm (0.057 to 0.132 m3/min) , and water pressure from 80 to 200 psi (5.52 x105 to 1.38 x106 pa). The effective limits for each control and interactions between these controls were of particular interest. Initial analysis concentrated on defining the impact of the control parameters on the respirable fraction of the feed dust, which was a blend containing 90% coal and 10% quartz. Gravimetric sampling indicated that airflow had the most significant individual impact on respirable dust levels and resulted in reductions of 99% at the operator and 57% in the return. Regression modeling was used to predict dust concentrations at the operator and in the return. Significant interactions were observed between control parameters and often, defined the level for a control parameter where increases above that level did not significantly benefit dust control. Increasing airflow to 8400 cfm (3.96 m3/sec), water flow to 25 gpm (0.095 m3/min), and water pressure to 140 psi (9.65 x105 Pa) typically provided respirable dust reductions at both sampling locations, while optimizing use of control resources. After determining these relationships for the total respirable fraction, selected filters were analyzed for quartz content to define the impact on the quartz component of the feed dust. For the individual control parameters, airflow again had the most significant impact and resulted in reductions of 98% at the operator and 26% in the return. Regression modeling of the quartz concentrations indicated that no significant interactions between control parameters were present. At the operators location, airflow was the only parameter identified as having a statistically significant reduction for quartz dust. A reduction in quartz approaching 95% was observed for increasing airflow to 6000 cfm (2.83 m3/sec). Increases above 6000 cfm had little additional impact. In the return, a linear relationship between control parameters and quartz levels was observed with reductions of approximately 27% predicted for increasing any one control parameter to its maximum level. The synergistic impact of increasing all control parameters to maximum levels resulted in a maximum predicted reduction of 81%.

Jan 1, 1991

By M. Imazu, Ö. Aydan

"A new rock classification, Rock Mass Quality Rating (RMQR) proposed by the authors is briefly explained and its application for the design of tunnels and large underground openings support systems is described in this paper. RMQR is an index to evaluate the state of rock mass. The preliminary support design may be based on the concept to prevent structurally controlled failures of rock mass. RMQR can also evaluate the yielding characteristics of rock masses so that it is possible to design a support system to prevent or control the deformation of surrounding rock through the utilization of the proposed rock mass classification and some analytical and numerical techniques.INTRODUCTIONThe first three authors proposed a new rock classification system named Rock Mass Quality Rating (RMQR) (Aydan et al. 2014). RMQR quantifies the rock mass state, and using the classification system together with intrinsic geo-mechanical properties of intact rock, possible geo-mechanical properties of rock masses can be estimated. The instability modes of underground openings can be structurally controlled because of the orientation of discontinuities in rock mass and the in-situ stress induced (Aydan 1989; Aydan et al. 1993, 1996; Aydan and Genis, 2010). The authors (Aydan and Ulusay, 2013; Aydan, 2016) have also tried to apply this system to the design of a tunnel support system. The authors presented initial guidelines for the RMQR classification system earlier (Aydan and Ulusay, 2013).In this paper, the authors provide further guidelines and establish some criteria for support system design that considers loading conditions and types of underground structure according to RMQR. Guidelines are alsos proposed for selecting the proper size of rockbolts, rock anchors, shotcrete, steel ribs and concrete liner. These guidelines are based on past experiences with various underground structures, theoretical understanding and the anticipated behavior of rock mass under given in-situ stress conditions and excavation techniques. The authors also utilized some databases developed for large underground caverns and tunnels excavated in squeezing or rock-bursting ground conditions."

Jan 1, 2016

By I. Kapageridis

The mining industry worldwide has recognized in the past the need to apply specific rules and guidelines in the reporting of mineral resources and reserves. The high financial investment and risk associated with any mining project and the ever stricter environmental and social controls were the forces behind this recognition. For years the industry experienced the development and enforcement of several codes for reporting accepted by different countries. The implementation of any code can be a confusing task as the guidelines are sometimes general and open to different interpretation. The use of computers in the estimation and reporting of mineral resources and reserves is necessary, particularly when trying to implement particular code guidelines. This paper discusses ways to implement a reporting code in a computerised resource/re-serve estimation study. The implementation is demonstrated using a gold deposit project as an example. The effects of mining, metallurgical, economic, marketing, legal, environmental, social and governmental factors are taken into consideration. This paper also discusses well established reporting codes and the possibility of reaching a single, universally applied code that could be used by Greek mining companies.

Jan 1, 2007

By Eleanor Sonley

In October 2000, temporary seismographic stations were installed above the Trail Mountain Mine, Emery County, Utah, USA to supplement a regional network. Over seven months, 1826 mining-induced seismic events were recorded with a magnitude range of M 0 to M 2.2 (Arabasz et al., 2002, 2005). Routine event locations for this dataset cluster around the longwall mining activity during the recording interval. However, applying a double difference relocation technique to the routine locations significantly improves the correlation between mining activity and event location. The resulting relocations depend greatly on station distribution and the number of arrival time picks. We use this dense temporary array to assess station distribution requirements for applying the double difference technique at other mines by systematically removing data from available stations, thus simulating sparser networks. The insight gained using the Trail Mountain dataset is used to develop a metric for assessing the usefulness of above-mine networks and to develop a tool for expanding seismic network coverage. To verify the appropriateness of these tools for wider application, we examine data from two additional mines located in the western United States. Improving the relative locations of mining-induced seismic events highlights the association of these events with active portions of the mine. Clusters, regions of quiescence and relative timing of events can be used by mine operators to assess hazard, optimize production, and evaluate performance of mine plans. The lessons learned from this study may be used in future network design to improve accuracy of event locations at other mines.

Jan 1, 2009

By G. H. Schnakenberg Jr.

In response to the underground mining industry's growing concern with the exposure of workers to the diesel particulate matter (DPM) component of diesel exhaust, a method was developed to estimate the average workplace concentration of DPM that could be expected from using the new lower DPMemitting engines now being approved by the US Mine Safety and Health Administration (MSHA) when these new engines are equipped with state-of-the-art exhaustcontrol technology for filtering and combusting DPM. The resulting estimate uses the MSHA-reported particulate index for these engines, the prevailing rule-of-thumb ventilation rate of 150 cfm/hp and the available diesel-exhaust filter technology that has been shown to be at least 80% effective in reducing tailpipe DPM. In the estimate calculation, every engine used in an underground mine is assumed to be equipped with this control technology. Under the stated reasonable conditions, an average DPM level of 90 µg/m3 (mass) is predicted as technically feasible.

Jan 1, 2002

By Steven I. Majtenyi

There is a growing interest among transportation planners to make more use of the subsurface to preserve the landscape and make transportation more efficient and economical. At the present time, utilization of the underground for transportation facilities is severely restrained by the adverse environmental impact and high construction costs. However, recent studies performed by the United States Department of Transportation indicate that, in spite of such problems, the volume of underground construction has significantly increased during recent years and projections point to continuation of these trends(1). It is estimated that the total volume of transportation tunnel construction will exceed $4 billion in this decade. This level of Investment justifies a significant research program. Due to the common interest in transportation tunnels and to the similarities of problems encountered during their construction, the tunneling research activities of the Federal Highway Administration (FHWA) are closely coordinated with the programs other agencies of the U. S. Department of Transportation DOT); specifically, the Federal Railroad Administration (PRA) and the Urban mass Transportation Administration (UMTA). The FHWA is responsive to the particular needs of these agencies but will benefit from the research results obtained also. In 1971, the Office of Secretary, DOT, initiated plans for an overall coordination of the DOT, FICA, UMTA, and FHWA tunneling research activities. The objectives of this effort have been to reduce tunneling costs by 30% and to increase the rate of excavation by 200% within 10 years. This coordinated program was developed and promoted during 1972 and 1973 by Dr. Eugene L. Foster, at that

Jan 1, 1974

By Palmer King

The increased emphasis on environmental protection, together with the exorbitant costs, or in many urban areas the complete unavailability of surface space, has resulted in a burgeoning demand for greater use of underground space. More and more, those considering new or expanded facilities are looking toward the possibility of utilizing underground space for communications installations, for transportation of people, industrial products, water, sewage and energy, and for industrial installations. Happily, this growing demand for use of underground space is accompanied by fast forward strides looking toward more efficient underground excavation techniques. The tunnel boring machine is already here and where ground conditions are suitable for its use it can greatly reduce the cost of underground excavations, savings of one-third or more often being realized. Research is underway involving excavation by use of laser beams, jetting, vibrations, improvement of tunnel boring machines to make possible the excavation of harder rock, and other advanced techniques. The Engineering Foundation estimated in 1973 that tunneling costs can be reduced as much as 30 percent by rapid excavation methods which are expected to be developed through ongoing research programs in the next few years. Your American Society of Civil Engineers reported in 1973 that $60 billion per year, or 15 percent of the gross national product, could be saved if facilities required to support life were located in the subsurface. Studies looking toward improved contracting practices are going on under the sponsorship of the National Academy of Sciences, and Mr. Al Mathews who is heading this program will address you during this session on the status of this project. I myself am a member of Mr. Mathews' study group and, considering the human element involved, it is too early to make predictions as to what can be accomplished in the way of savings in costs of

Jan 1, 1974

By J. D. Morgan

The US economy continued to grow steadily in 1988, reaching an annual rate of $5 trillion in the last quarter (US trillion = 1012). The value of domestically processed mineral-based materi¬als rose 20% to $300 billion (US billion 109). The value of metals produced from US ores rose 40% to more than $10 billion, industrial minerals rose 6%' to $20 billion, and recycled scrap more than doubled to $10 billion. Increasing economic activity stimulated metal prices. Yearly lows and highs were 95 cents and $1.68 for copper, 52 cents, and $1.30 for aluminum, 34 cents and 42 cents for lead, and 43 cents and 75 cents for zinc. A number of mining and metal companies experienced significantly increased profitability. Consumer demand strongly affects mining because the US economy is relatively saturated with long-lived products. Consumer, mortgage, and Federal debt continued to rise. About 246 million US citizens already possess 170 million licensed motor vehicles and 100 million dwelling units. New car production remained at the 1987 level of 7.1 million units. Truck and bus production, however, rose 7% to 4.1 million units. New housing starts fell 7% to 1.5 million units. Imports supplied a significant proportion of total US consumption of several important mineral materials. By year-end, imports of crude and refined petroleum exceeded domestic crude oil production. Such imports cost $42 billion. Imports of nonfuel mineral-based materials were valued at $44 billion and exports at $35 billion. The US and Canada-the world's two largest trading partners-consummated a historic free trade agreement. In February, President Reagan transferred responsibility for stockpiling strategic and critical materials to the Secretary of Defense. And, in July, the GSA group that bought, stored, rotated, and sold stockpiled materials was transferred to the Defense Department's Defense Logistics Agency. Concern about apartheid in South Africa continued, resulting in increasing attention to chromium, manganese, platinum-group metals, cobalt, vanadium, and gold. The Defense Production Act, authorizing priorities and allocations, supply expansions, voluntary agreements, and the National Defense Executive Reserve, was amended to include provisions for averting harm to national security from foreign takeovers. The DPAct, in effect through September 1989, is now up for further extension. Under the Act, the US Bureau of Mines maintains the Emergency Minerals Administration. During the year, consultations were held with Canada to strengthen the North American Defense Industrial Base. Coal production, 60% from open pits, rose 5% to 870 Mt (960 million st). Nearly four-fifths was burned to generate 57% of US electricity. Exports included 56 Mt (62 million st) of metallur- gical coal and 29 Mt (32 million st) of steam coal, with a total value of $4 billion. Domestic petroleum produc¬tion fell 2% to 574 hm3 (3.6 billion bbl). Uranium mining, including recovery from phosphates, was unchanged at 5.9 kt (6500 st). Nonfuel minerals Major metals Raw steel production-a major con¬sumer of many minerals-rose 14% to 92 Mt (102 million st). Domestic iron ore production rose 25% to 59 Mt (65 million st), about 96% pelletized. Net imports rose 37% to 16 Mt (18 million st). Raw steelmaking capacity of 102 Mt (112 million st) was unchanged. Voluntary Restraint Agreements with 21 steel exporting nations limited im¬port penetration to about 20% of the domestic market. Domestic producers of bulk ferroal¬loys of chromium, manganese, and sili¬con operated at about 75% of capacity. The US mined no manganese or chro-

Jan 1, 1989

By N. Colvin, J. W. Gulyas

HISTORY The Surigao Nickel Refinery of Marinduque Mining and Industrial Corporation is located on Nonoc Island off the northwestern coast of Mindanao in the Philippines. Nonoc Island is part of the Surigao Mineral Reservation which had been identified as early as 1912. Initial interest in these deposits was due to their iron content, and their value as a nickel deposit was not seriously entertained until the late 1950's. The Philippine government undertook extensive test pitting and sampling programmes at that time and in the early sixties Marinduque became involved in helping to establish firmer ore reserves. Evaluations of the test pitting programme indicated reserves of 75,000,000 tonnes of ore averaging 1.22% Ni, 0.1% Co and 38.5% Fe. The Philippine government called for bids on the reservation in 1962 and Marinduque and Sherritt Gordon carried out some feasibility studies for the recovery of nickel from the deposit. However, it was not until 1968 that Marinduque was granted proper authority to exploit the Surigao deposits. Marinduque and Sherritt then entered into an agreement which allowed Marinduque to utilize a process developed by Sherritt for treating lateritic ores. During 1968, a 25 st/d pilot plant was erected in Fort Saskatchewan, Alberta for the purpose of modelling all process steps. A 10,000 tonne ore sample was sent from Nonoc as feed stock for the pilot plant.

Jan 1, 1979

By V. C. Kelessidis

Demand for multifunctional drilling fluids continuously increases. In the quest for more hydrocarbons, drilling has extended to deep water areas (now in excess of 2.000 m) and to very deep wells (now in excess of 6.000 m). In these extreme conditions, low temperatures, as low as 1-5°C on the sea bed, high temperatures, in excess of 200°C, and high pressures, more than 1.000 bars, in the bottom of the well, are frequently encountered. In these harsh environments, synthetic oil and oil based drilling fluids are used, but the former are expensive while strict environmental requirements have limited the use of the latter. Thus, drilling industry has turned back to water based drilling fluids which use bentonite as primary viscosifier and as a fluid loss control additive. However, in conditions of high temperatures, bentonite suspensions gel and loose their exceptional low temperatures properties, thus, additives are needed to overcome such problems. In this article we review these challenging drilling environments and establish the requirements for the multifunctional drilling fluids. Our research indicates that demand for continuing use of bentonite by drilling fluid industry is strong. Furthermore, we bring forward the opportunities for new additive development which can expand the operational ranges of bentonite suspensions.

Jan 1, 2007

By Greg Bold, Mahmood Khwaja, Yuannian (Jerry) Wan, Michael S. Schultz, William Simcoe

Beaver Creek Clean River Project will satisfy the consent decree requirements by capturing and treating combined sewage overflows. The project consists of, approximately, 2,700 feet of 30-inch trenchless pipe installation, a new screening/disinfecting facility, an expansion of an existing diversion structure, and a 72-inch internal diameter, 530-foot long mined tunnel. The tunnel portions are being progressed as early release packages. This paper presents the geotechnical exploration program and the subsurface conditions encountered; interpretation of the geotechnical conditions; and, approach to developing stand-alone packages for the tunnels to mitigate construction and schedule risks and continue to advance the project.

Jun 13, 2021

By Nora M. Hutt, Kevin A. Morin

One technique for controlling ongoing acidic drainage is to relocate and submerge net-acid-generating waste rock in a lake or water-retaining impoundment. This can lead to the overall improvement of water quality and the reduction In short-term environmental liabilities. A case study of this technique is the Eskay Creek Mine in northern British Columbia. Some findings of the study are: (1) the addition of lime to each truckload of rock, based on its rinse pH, neutralized the accumulated acidity and suppressed the accumulated-metal release, (2) only 10-20% of the dump's neutralization potential had been consumed when acidic drainage appeared, (3) water chemistry in the watershed recovered roughly three years after relocation, and (4) environmental liability was reduced due to the cessation of on-land acidic drainage with no degradation of lake chemistry.

Jan 1, 2000